Monte Carlo comparison of x-ray and proton CT for range calculations of proton therapy beams
Monte Carlo comparison of x-ray and proton CT for range calculations of proton therapy beams
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DOI：
10.1088/0031-9155/60/19/7585
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发表时间：
2015-10-07
影响因子：
3.5
通讯作者：
Rit, S.
中科院分区：
文献类型：
--
作者：
Arbor, N.;Dauvergne, D.;Rit, S.
质子计算机断层扫描(CT)被描述为一种用于成像患者组织的质子阻止能力的解决方案，从而减少了将X射线CT图像转换为相对阻止能力(RSP)图及其相关边缘的不确定性。本研究的目的是在理想检测系统的假设下对这一断言进行研究。我们开发了一个蒙特卡罗框架来评估质子治疗治疗计划的主要步骤的质子CT性能，即质子或X射线CT成像，基于组织体模的校准转换为RSP图，以及质子剂量模拟。用铅笔束模拟计算体模在不同解剖位置的照射，并在参考材料图、基于质子CT的材料图和基于X射线CT的材料图上评估质子射程。从质子CT重建的组织RSP的误差被发现要小得多，而且对组织分布的依赖程度较低。成像剂量也被发现更加均匀和与主光束共形。基于X射线CT的射程计算的平均绝对偏差在0.18-2.01 mm之间，而质子CT的平均绝对偏差小于0.1 mm。因此，在完美探测系统的假设下，基于质子CT的质子射程预测比基于X射线CT的质子射程预测更准确和更一致。
Proton computed tomography (CT) has been described as a solution for imaging the proton stopping power of patient tissues, therefore reducing the uncertainty of the conversion of x-ray CT images to relative stopping power (RSP) maps and its associated margins. This study aimed to investigate this assertion under the assumption of ideal detection systems. We have developed a Monte Carlo framework to assess proton CT performances for the main steps of a proton therapy treatment planning, i.e. proton or x-ray CT imaging, conversion to RSP maps based on the calibration of a tissue phantom, and proton dose simulations. Irradiations of a computational phantom with pencil beams were simulated on various anatomical sites and the proton range was assessed on the reference, the proton CT-based and the x-ray CT-based material maps. Errors on the tissue's RSP reconstructed from proton CT were found to be significantly smaller and less dependent on the tissue distribution. The imaging dose was also found to be much more uniform and conformal to the primary beam. The mean absolute deviation for range calculations based on x-ray CT varies from 0.18 to 2.01 mm depending on the localization, while it is smaller than 0.1 mm for proton CT. Under the assumption of a perfect detection system, proton range predictions based on proton CT are therefore both more accurate and more uniform than those based on x-ray CT.